ShrinkWrapv14

Hunt Hypothesis

This detection identifies potential file compression or obfuscation activities consistent with the ShrinkWrapv14 signature, which adversaries often employ to conceal malicious payloads within legitimate archives. Proactively hunting for this behavior in Azure Sentinel allows the SOC team to uncover stealthy initial access mechanisms that may evade standard signature-based defenses by analyzing compressed artifacts before they are executed on endpoints.

YARA Rule

rule ShrinkWrapv14
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 58 60 8B E8 55 33 F6 68 48 01 [2] E8 49 01 [2] EB }

condition:
		$a0 at pe.entry_point
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the ShrinkWrapv14 detection rule in an enterprise environment, along with recommended filters and exclusions:

• Scenario: Legitimate deployment of Java-based applications via Ansible Tower or Jenkins CI/CD pipelines.

  • Context: During automated build and release windows, the orchestration engine extracts .war or .jar archives containing ShrinkWrap artifacts to temporary staging directories before deployment. The YARA rule triggers on the extraction of these specific bytecode structures.
  • Filter/Exclusion: Exclude file paths matching C:\Jenkins\workspace\* and D:\Ansible\temp\_deploy_*. Additionally, add a process exclusion for java.exe when launched by parent processes jenkins-agent.exe or ansible-runner.exe.

• Scenario: Scheduled daily backup and archiving jobs using Veeam Backup & Replication or Commvault.

  • Context: The backup agent scans the file system to identify incremental changes. When processing large application directories (e.g., Oracle Home or Tomcat instances), the agent reads ShrinkWrap-embedded libraries, causing the YARA signature to match the read operation as a potential new artifact creation event.
  • Filter/Exclusion: Create an exclusion for file operations occurring on network shares mounted by VeeamBackupService and CommServe.exe. Filter out events where the process name contains “backup” or “agent” during standard maintenance windows (e.g., 02:00–06:00 UTC).

• Scenario: Execution of internal compliance scanning tools like Qualys Cloud Agent or Tenable Nessus.

  • Context: These agents perform deep file system scans to detect software inventory and configuration drift. When the agent parses Java runtime environments, it triggers the